Apparatus and method for establishing g maintenance routes within a process control system

ABSTRACT

Generating a maintenance route in a process control system includes creating an initial ordered list of all wireless nodes in direct communication with a wireless gateway, where the nodes are ordered by signal strength with the wireless gateway device. A subsequent ordered list is created of all nodes in direct communication with first node of the initial ordered list, where the nodes are ordered by signal strength with the first node. The subsequent ordered list is then appended to the initial ordered list after the first node. This process of creating a subsequent list and appending the initial list is iteratively repeated thereafter, each time accounting for the next node in the appended ordered list following the previous iteration until all nodes are accounted for. In the last iteration, the nodes correspond to stop points along the route and the order corresponds to the route to be taken among the stop points.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of pending U.S. patentapplication Ser. No. 13/362,476, filed Jan. 31, 2012, and entitled“APPARATUS AND METHOD FOR ESTABLISHING MAINTENANCE ROUTES WITHIN APROCESS CONTROL SYSTEM,” the entirety of which is incorporated byreference herein in its entirety.

FIELD OF THE TECHNOLOGY

The present disclosure relates generally to process control systemswithin process plants and, more particularly, to dynamically generatingand updating maintenance routes in a process control system having awireless network based on network topology.

BACKGROUND

Process control systems are widely used in factories and/or plants inwhich products are manufactured or processes are controlled (e.g.,chemical manufacturing, power plant control, etc.). Process controlsystems are also used in the harvesting of natural resources such as,for example, oil and gas drilling and handling processes, etc. In fact,virtually any manufacturing process, resource harvesting process, etc.can be automated through the application of one or more process controlsystems. It is believed the process control systems will eventually beused more extensively in agriculture as well.

Process control systems, like those used in chemical, petroleum or otherprocesses, typically include one or more centralized or decentralizedprocess controllers communicatively coupled to at least one host oroperator workstation and to one or more process control andinstrumentation devices, such as field devices, via analog, digital orcombined analog/digital buses. Field devices, which may be, for examplevalves, valve positioners, switches, transmitters, and sensors (e.g.,temperature, pressure and flow rate sensors), perform functions withinthe process such as opening or closing valves and measuring processparameters. The process controller receives signals indicative ofprocess measurements or process variables made by or associated with thefield devices and/or other information pertaining to the field devices,uses this information to implement a control routine and then generatescontrol signals which are sent over one or more of the buses to thefield devices to control the operation of the process. Information fromthe field devices and the controller is typically made available to oneor more applications executed by an operator workstation to enable anoperator to perform desired functions with respect to the process, suchas viewing the current state of the process, modifying the operation ofthe process, etc.

The various devices within the process plant may be interconnected inphysical and/or logical groups to create a logical process, such as acontrol loop. Likewise, a control loop may be interconnected with othercontrol loops and/or devices to create sub-units. A sub-unit may beinterconnected with other sub-units to create a unit, which in turn, maybe interconnected with other units to create an area. Process plantsgenerally include interconnected areas, and business entities generallyinclude process plants which may be interconnected. As a result, aprocess plant includes numerous levels of hierarchy havinginterconnected assets, and a business enterprise may includeinterconnected process plants. In other words, assets related to aprocess plant, or process plants themselves, may be grouped together toform assets at higher levels.

The manner in which process control systems are implemented has evolvedover the years. Older generations of process control systems weretypically implemented using dedicated, centralized hardware andhard-wired connections.

However, modern process control systems are typically implemented usinga highly distributed network of workstations, intelligent controllers,smart field devices, and the like, some or all of which may perform aportion of an overall process control strategy or scheme. In particular,most modern process control systems include smart field devices andother process control components that are communicatively coupled toeach other and/or to one or more process controllers via one or moredigital data buses. In addition to smart field devices, modern processcontrol systems may also include analog field devices such as, forexample, 4-20 milliamp (mA) devices, 0-10 volts direct current (VDC)devices, etc., which are typically directly coupled to controllers asopposed to a shared digital data bus or the like.

In a typical industrial or process plant, a distributed control system(DCS) is used to control many of the industrial processes performed atthe plant. The plant may have a centralized control room having acomputer system with user input/output (I/O), a disc I/O, and otherperipherals known in the computing art with one or more processcontrollers and process I/O subsystems communicatively connected to thecentralized control room. Additionally, one or more field devices aretypically connected to the I/O subsystems and to the process controllersto implement control and measurement activities within the plant. Whilethe process I/O subsystem may include a plurality of I/O ports connectedto the various field devices throughout the plant, the field devices mayinclude various types of analytical equipment, silicon pressure sensors,capacitive pressure sensors, resistive temperature detectors,thermocouples, strain gauges, limit switches, on/off switches, flowtransmitters, pressure transmitters, capacitance level switches, weighscales, transducers, valve positioners, valve controllers, actuators,solenoids, indicator lights or any other device typically used inprocess plants.

As used herein, the term “field device” encompasses these devices, aswell as any other device that performs a function in a control system.In any event, field devices may include, for example, input devices(e.g., devices such as sensors that provide status signals that areindicative of process control parameters such as, for example,temperature, pressure, flow rate, etc.), as well as control operators oractuators that perform actions in response to commands received fromcontrollers and/or other field devices.

Traditionally, analog field devices have been connected to thecontroller by two-wire twisted pair current loops, with each deviceconnected to the controller by a single two-wire twisted pair. Analogfield devices are capable of responding to or transmitting an electricalsignal within a specified range. In a typical configuration, it iscommon to have a voltage differential of approximately 20-25 voltsbetween the two wires of the pair and a current of 4-20 mA runningthrough the loop. An analog field device that transmits a signal to thecontrol room modulates the current running through the current loop,with the current being proportional to the sensed process variable.

An analog field device that performs an action under control of thecontrol room is controlled by the magnitude of the current through theloop, which current is modulated by the I/O port of the process I/Osystem, which in turn is controlled by the controller. Traditionaltwo-wire analog devices having active electronics can also receive up to40 milliwatts of power from the loop. Analog field devices requiringmore power are typically connected to the controller using four wires,with two of the wires delivering power to the device. Such devices areknown in the art as four-wire devices and are not power limited, astypically are two-wire devices.

A discrete field device can transmit or respond to a binary signal.Typically, discrete field devices operate with a 24 volt signal (eitherAC or DC), a 110 or 240 volt AC signal, or a 5 volt DC signal. Ofcourse, a discrete device may be designed to operate in accordance withany electrical specification required by a particular controlenvironment. A discrete input field device is simply a switch whicheither makes or breaks the connection to the controller, while adiscrete output field device will take an action based on the presenceor absence of a signal from the controller.

Historically, most traditional field devices have had either a singleinput or a single output that was directly related to the primaryfunction performed by the field device. For example, the only functionimplemented by a traditional analog resistive temperature sensor is totransmit a temperature by modulating the current flowing through thetwo-wire twisted pair, while the only function implemented by atraditional analog valve positioner is to position a valve somewherebetween a fully open and a fully closed position based on the magnitudeof the current flowing through the two-wire twisted pair.

More recently, field devices that are part of hybrid systems becomeavailable that superimpose digital data on the current loop used totransmit analog signals. One such hybrid system is known in the controlart as the Highway Addressable Remote Transducer (HART) protocol. TheHART system uses the magnitude of the current in the current loop tosend an analog control signal or to receive a sensed process variable(as in the traditional system), but also superimposes a digital carriersignal upon the current loop signal. The HART protocol makes use of theBell 202 Frequency Shift Keying (FSK) standard to superimpose thedigital signals at a low level on top of the 4-20 mA analog signals.This enables two-way field communication to take place and makes itpossible for additional information beyond just the normal processvariable to be communicated to/from a smart field instrument. The HARTprotocol communicates at 1200 bps without interrupting the 4-20 mAsignal and allows a host application (master) to get two or more digitalupdates per second from a field device. As the digital FSK signal isphase continuous, there is no interference with the 4-20 mA signal.

The FSK signal is relatively slow and can therefore provide updates of asecondary process variable or other parameter at a rate of approximately2-3 updates per second. Generally, the digital carrier signal is used tosend secondary and diagnostic information and is not used to realize theprimary control function of the field device. Examples of informationprovided over the digital carrier signal include secondary processvariables, diagnostic information (including sensor diagnostics, devicediagnostics, wiring diagnostics, and process diagnostics), operatingtemperatures, a sensor temperature, calibration information, device IDnumbers, materials of construction, configuration or programminginformation, etc. Accordingly, a single hybrid field device may have avariety of input and output variables and may implement a variety offunctions.

More recently, a newer control protocol has been defined by theInstrument Society of America (ISA). The new protocol is generallyreferred to as Fieldbus, and is specifically referred to as SP50, whichis as acronym for Standards and Practice Subcommittee 50. The Fieldbusprotocol defines two subprotocols. An H1 Fieldbus network transmits dataat a rate up to 31.25 kilobits per second and provides power to fielddevices coupled to the network. An H2 Fieldbus network transmits data ata rate up to 2.5 megabits per second, does not provide power to fielddevices connected to the network, and is provided with redundanttransmission media. Fieldbus is a nonproprietary open standard and isnow prevalent in the industry and, as such, many types of Fieldbusdevices have been developed and are in use in process plants. BecauseFieldbus devices are used in addition to other types of field devices,such as HART and 4-20 mA devices, with a separate support and I/Ocommunication structure associated with each of these different types ofdevices.

Newer smart field devices, which are typically all digital in nature,have maintenance modes and enhanced functions that are not accessiblefrom or compatible with older control systems. Even when all componentsof a distributed control system adhere to the same standard (such as theFieldbus standard), one manufacturer's control equipment may not be ableto access the secondary functions or secondary information provided byanother manufacturer's field devices.

Thus, one particularly important aspect of process control system designinvolves the manner in which field devices are communicatively coupledto each other, to controllers and to other systems or devices within aprocess control system or a process plant. In general, the variouscommunication channels, links and paths that enable the field devices tofunction within the process control system are commonly collectivelyreferred to as an input/output (I/O) communication network.

The communication network topology and physical connections or pathsused to implement an I/O communication network can have a substantialimpact on the robustness or integrity of field device communications,particularly when the I/O communications network is subjected toenvironmental factors or conditions associated with the process controlsystem. For example, many industrial control applications subject fielddevices and their associated I/O communication networks to harshphysical environments (e.g., high, low or highly variable ambienttemperatures, vibrations, corrosive gases or liquids, etc.), difficultelectrical environments (e.g., high noise environments, poor powerquality, transient voltages, etc.), etc. In any case, environmentalfactors can compromise the integrity of communications between one ormore field devices, controllers, etc. In some cases, such compromisedcommunications could prevent the process control system from carryingout its control routines in an effective or proper manner, which couldresult in reduced process control system efficiency and/orprofitability, excessive wear or damage to equipment, dangerousconditions that could damage or destroy equipment, building structures,the environment and/or people, etc.

In order to minimize the effect of environmental factors and to assure aconsistent communication path, I/O communication networks used inprocess control systems have historically been hardwired networks, withthe wires being encased in environmentally protected materials such asinsulation, shielding and conduit. Also, the field devices within theseprocess control systems have typically been communicatively coupled tocontrollers, workstations, and other process control system componentsusing a hardwired hierarchical topology in which non-smart field devicesare directly coupled to controllers using analog interfaces such as, forexample, 4-20 mA, 0-10 VDC, etc. hardwired interfaces or I/O boards.Smart field devices, such as Fieldbus devices, are also coupled viahardwired digital data busses, which are coupled to controllers viasmart field device interfaces.

While hardwired I/O communication networks can initially provide arobust I/O communication network, their robustness can be seriouslydegraded over time as a result of environmental stresses (e.g.,corrosive gases or liquids, vibration, humidity, etc.). For example,contact resistances associated with the I/O communication network wiringmay increase substantially due to corrosion, oxidation and the like. Inaddition, wiring insulation and/or shielding may degrade or fail,thereby creating a condition under which environmental electricalinterference or noise can more easily corrupt the signals transmittedvia the I/O communication network wires. In some cases, failedinsulation may result in a short circuit condition that results in acomplete failure of the associated I/O communication wires.

Additionally, hardwired I/O communication networks are typicallyexpensive to install, particularly in cases where the I/O communicationnetwork is associated with a large industrial plant or facility that isdistributed over a relatively large geographic area, for example, an oilrefinery or chemical plant that consumes several acres of land. In manyinstances, the wiring associated with the I/O communication network mustspan long distances and/or go through, under or around many structures(e.g., walls, buildings, equipment, etc.) Such long wiring runstypically involve substantial amounts of labor, material and expense.Further, such long wiring runs are especially susceptible to signaldegradation due to wiring impedances and coupled electricalinterference, both of which can result in unreliable communications.

Moreover, such hardwired I/O communication networks are generallydifficult to reconfigure when modifications or updates are needed.Adding a new field device typically requires the installation of wiresbetween the new field device and a controller. Retrofitting a processplant in this manner may be very difficult and expensive due to the longwiring runs and space constraints that are often found in older processcontrol plants and/or systems. High wire counts within conduits,equipment and/or structures interposing along available wiring paths,etc., may significantly increase the difficulty associated withretrofitting or adding field devices to an existing system. Exchangingan existing field device with a new device having different field wiringrequirements may present the same difficulties in the case where moreand/or different wires have to be installed to accommodate the newdevice. Such modifications may often result in significant plantdowntime.

Wireless I/O communication networks have been used to alleviate some ofthe difficulties associated with hardwired I/O networks, and toalleviate the costs involved in deploying sensors and actuators withinthe process control system. Wireless I/O communication networks havealso been suggested for process control systems and portions thereofthat are relatively inaccessible or inhospitable for hardwired I/Ocommunication networks. For example, Shepard et al., U.S. Pat. No.7,436,797 entitled “Wireless Architecture And Support For ProcessControl Systems” and patented Oct. 14, 2008, the content of which isexpressly incorporated by reference herein, discloses that relativelyinexpensive wireless mesh networks may be deployed within a processcontrol system, either alone or in combination with point-to-pointcommunications, to produce a robust wireless communication network thatcan be easily set up, configured, changed and monitored, to thereby makethe wireless communication network more robust, less expensive and morereliable.

Wireless mesh networks (or mesh networking topology) utilize multiplenodes, each of which may serve not only as a client to receive and sendits own data, but also as a repeater or relay to propagate data throughthe network to other nodes. Each node is connected to anotherneighboring node, and preferably to multiple neighboring nodes, each ofwhich may be connected to additional neighboring nodes. The result is anetwork of nodes that provides multiple paths of communication from onenode to another through the network, thereby creating a relativelyinexpensive, robust network that allows for continuous connections andreconfigurations even when communication paths are broken or blocked.

In a wireless mesh network, each device (node) may connect to a gatewayvia direct wireless connection or indirectly via a connection through aneighboring device. Each device has a signal strength that generallycorrelates to the physical proximity of the device to the wirelessgateway or to a neighboring device. In cases where no direct connectionto the wireless gateway is available, each device connects to thegateway through another peer device that has a connection to the gatewayor to another device. The number of devices used to chain together aconnection of a device to the gateway is known as the number of hops ina connection path. Each device uses the connection path, and the orderin which the device-to-device connections are established is known asthe communication route.

Regardless of the type of network implemented within a process system,maintenance personnel are tasked with maintaining and calibrating thedevices within the network. This means physically walking through theprocess plant from device to device according to an ordered list of stoppoints to perform necessary data gathering, maintenance and calibrationactivities. Traditionally, route-based maintenance software applicationshave utilized a process for establishing maintenance routes usingknowledge of the physical location of the devices and the specificationof where the stop points are along a defined route. The route containedan ordered list of stop points that an engineer or other maintenancepersonnel walked through to perform tasks related to gathering data,calibrating devices, performing maintenance on the device or performinga visual inspection of the device. While the defined route was intendedto provide the most efficient path to perform these tasks, itnonetheless relied upon a manual process for deciding which tasks occuralong a given path in the route. That is, while route-based maintenancesoftware applications generated work orders for the maintenancepersonnel, the routes used by the maintenance personnel were generatedmanually, often relying on the knowledge of the physical location of thedevices and the stop points. Not only was this an inefficient use of themaintenance personnel's time, particularly where the devices and stoppoints may number in the dozens or hundreds, but the manually-createdroutes were not necessarily the most optimal or efficient, and weresometimes vastly sub-optimal.

SUMMARY

Signal strength and communication paths within a wireless network areutilized to automatically establish a maintenance route for maintenanceor other plant personnel to perform device calibration, data gathering,equipment inspection or other maintenance activities as defined in themaintenance route. The process by which the maintenance route isestablished is based on a sequence of calculations taking into accountthe proximity of each device with the wireless gateway and/or withrespect to neighboring devices. The proximity is inferred from thesignal strength with the wireless gateway and/or with neighboringdevices, and the number of hops that occur in the communication path fora given set of devices communicating in the network. Taking into accountall devices communicating with the wireless gateway either directly orvia another device, a ordered list of all devices with zero hops intheir communication path (i.e., directly communicating with the gateway)is created, where the devices are ordered by signal strength with thewireless gateway. Beginning with the first device in the list, a furtherordered list is created of neighboring devices in direct communicationwith the first device, and the further ordered list is appended to theinitial ordered list after the first device. This process of creating afurther ordered list and appending the initial ordered list isiteratively repeated thereafter, each time accounting for the nextdevice in the appended ordered list following the previous iterationuntil all devices are accounted for. Once all devices communicating withthe wireless gateway, either directly or via another device, areaccounted for, the devices in the list correspond to stop points alongthe route and the order of the devices in the list corresponds to theroute to be taken among the stop points.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a combined block and schematic diagram of a distributedcontrol system in accordance with this disclosure;

FIG. 2 is a combined block and schematic diagram of a wirelesscommunication network within a portion of a process environment inaccordance with this disclosure;

FIG. 3 is a schematic diagram of a wireless communication environment inwhich a wireless network includes a plurality of nodes corresponding tovarious field devices;

FIGS. 4A and 4B are charts presented in tabular form illustratingwireless mesh network and wireless point-to-point topographies of nodesand corresponding neighboring nodes in order of proximity;

FIG. 5 is a flowchart of a maintenance route generation routine inaccordance with this disclosure;

FIGS. 6A-6E are illustrations of the generation and progression ofordered lists generated from the routine of FIG. 5 as the routineexecutes various iterations of the lists for a wireless mesh network;

FIG. 7 is a flowchart of a routine from FIG. 5 for creating an orderedlist of nodes in direct communication with a gateway;

FIG. 8 is a flowchart of a routine from FIG. 5 for iteratively creatingordered lists of nodes in direct communication with a node from the listgenerated by the routine of FIG. 7 and as appended by the flowchart ofFIG. 9;

FIG. 9 is a flowchart of a routine from FIG. 5 for appending the listgenerated from the routine of FIG. 7 and as appended in previousiterations of the routine of FIG. 5;

FIG. 10 is a schematic diagram showing a maintenance route through thewireless mesh network communication environment of FIG. 3 as generatedby the routine of FIG. 5;

FIGS. 11A-11E are illustrations of the generation and progression ofordered lists generated from the routine of FIG. 5 as the routineexecutes various iterations of the lists for a wireless point-to-pointnetwork; and

FIG. 12 is a schematic diagram showing a maintenance route through thewireless point-to-point network communication environment of FIG. 3 asgenerated by the routine of FIG. 5.

DETAILED DESCRIPTION

Referring now to FIG. 1, a hardwired distributed process control system10 includes one or more process controllers 12 connected to one or morehost workstations or computers 14 (which may be any type of personalcomputer or workstation). The process controllers 12 are also connectedto banks of input/output (I/O) devices 20, 22 each of which, in turn, isconnected to one or more field devices 25-39. The controllers 12, whichmay be, by way of example only, DeltaV™ controllers sold byFisher-Rosemount Systems, Inc., are communicatively connected to thehost computers 14 via, for example, an Ethernet connection 40 or othercommunication link. Likewise, the controllers 12 are communicativelyconnected to the field devices 25-39 using any desired hardware andsoftware associated with, for example, standard 4-20 ma devices and/orany smart communication protocol such as the Fieldbus or HART protocols.As is generally known, the controllers 12 implement or oversee processcontrol routines stored therein or otherwise associated therewith andcommunicate with the devices 25-39 to control a process in any desiredmanner.

The field devices 25-39 may be any types of devices, such as sensors,valves, transmitters, positioners, etc. while the I/O cards within thebanks 20 and 22 may be any types of I/O devices conforming to anydesired communication or controller protocol such as HART, Fieldbus,Profibus, etc. In the embodiment illustrated in FIG. 1, the fielddevices 25-27 are standard 4-20 mA devices that communicate over analoglines to the I/O card 22A. The field devices 28-31 are illustrated asHART devices connected to a HART compatible I/O device 20A. Similarly,the field devices 32-39 are smart devices, such as Fieldbus fielddevices, that communicate over a digital bus 42 or 44 to the I/O cards20B or 22B using, for example, Fieldbus protocol communications. Ofcourse, the field devices 25-39 and the banks of I/O cards 20 and 22could conform to any other desired standard(s) or protocols besides the4-20 mA, HART or Fieldbus protocols, including any standards orprotocols developed in the future.

Each of the controllers 12 is configured to implement a control strategyusing what are commonly referred to as function blocks, wherein eachfunction block is a part (e.g., a subroutine) of an overall controlroutine and operates in conjunction with other function blocks (viacommunications called links) to implement process control loops withinthe process control system 10. Function blocks typically perform one ofan input function, such as that associated with a transmitter, a sensoror other process parameter measurement device, a control function, suchas that associated with a control routine that performs PID, fuzzylogic, etc. control, or an output function that controls the operationof some device, such as a valve, to perform some physical functionwithin the process control system 10. Of course hybrid and other typesof function blocks exist. Groups of these function blocks are calledmodules. Function blocks and modules may be stored in and executed bythe controller 12, which is typically the case when these functionblocks are used for, or are associated with standard 4-20 mA devices andsome types of smart field devices, or may be stored in and implementedby the field devices themselves, which may be the case with Fieldbusdevices. While the control system 10 illustrated in FIG. 1 is describedas using function block control-strategy, the control strategy couldalso be implemented, or designed using other conventions, such as ladderlogic, sequential flow charts, etc. and using any desired proprietary ornon-proprietary programming language.

Still further, in a known manner, one or more of the workstations 14 mayinclude user interface applications to enable a user, such as anoperator, a configuration engineer, a maintenance person, etc. tointerface with the process control network 10 within the plant. Inparticular, the workstation 14 may include one or more user interfaceapplications which may be executed on a processor within the workstation14 to communicate with a database, the control modules or other routineswithin the controllers 12 or I/O banks 20, 22, with the field devices25-39 and the modules within these field devices, etc. to obtaininformation from the plant, such as information related to the ongoingstate of the process control system 10. The user interface applicationsmay process and/or display this collected information on a displaydevice associated with one or more of the workstations 14. Thecollected, processed and/or displayed information may be, for example,process state information, alarms and alerts generated within plant,maintenance data, etc. Likewise, one or more applications may be storedin an executed in the workstations 14 to perform configurationactivities such as creating or configuring the modules to be executedwithin the plant, to perform control operator activities, such aschanging set-points or other control variables, within the plant, etc.Of course the number and type of routines is not limited by thedescription provided herein and other numbers and types of processcontrol related routines may be stored in an implemented within theworkstations 14 if desired. The workstations 14 may also be connectedvia, for example, the internet, extranet, bus, Ethernet 40, etc., to acorporate WAN as well as to a computer system that enables remotemonitoring of or communication with the plant 10 from remote locations.

As evident from the discussion of FIG. 1, the communications between thehost workstations 14 and the controllers 12 and between the controllers12 and the field devices 25-39 are implemented with hardwiredcommunication connections, including one or more of HART, Fieldbus and4-20 mA hardwired communication connections. However, as noted above,the hardwired communication connections may be replaced or augmentedwithin the process environment of FIG. 1 with wireless communications inan manner that is reliable, that is easy to set up and configure, thatprovides an operator or other user with the ability to analyze or viewthe functioning capabilities of the wireless network, etc.

For example, wireless networks may be deployed throughout the processcontrol system as disclosed in U.S. Pat. No. 7,436,797 incorporated byreference above. As a result, some or all of the I/O devices within aprocess control system, such as sensors and actuators, may be deployedand communicatively coupled to the process control system usinghardwired technologies, wireless technologies or combination thereof.For example, hardwired communications may be maintained between andamong some of the controllers 12, the workstations 14, and the fielddevices 25-31, whereas wireless communications may be establishedbetween and among others of the controllers 12, the workstations 14, andfield devices 32-39. Wireless technologies may include, but are notlimited to, ZigBee, WiFi, Bluetooth, Ultra Wideband (UWB), etc., or anyother short-range wireless technology, as well as satellite, Wi-Max, andother long-range wireless transmission. In particular, wirelesstechnologies may include any commercial off-the-shelf wireless productsto transmit process control data. A network protocol may be implementedon top of the wireless technology, or a new process control standard maybe developed for wireless communication. In one example, meshtechnologies, such as a self-healing/self-organizing ad hoc wirelessmesh technology, may be implemented.

FIG. 2 illustrates a wireless communication network 60 that may be usedto provide communications between the different devices illustrated inFIG. 1 and, in particular, between the controllers 12 (or the associatedI/O devices 22) of FIG. 1 and the field devices 25-39, between thecontrollers 12 and the host workstations 14 or between the hostworkstations 14 and the field devices 25-39 of FIG. 1. However, it willbe understood that the wireless communication network 60 of FIG. 2 couldbe used to provide communications between any other types or sets ofdevices within a process plant or a process environment.

The communication network 60 of FIG. 2 is illustrated as includingvarious communication nodes including one or more base nodes 62, one ormore repeater nodes 64, one or more environment nodes 66 (illustrated inFIG. 2 as nodes 66 a and 66 b) and one or more field nodes 68(illustrated in FIG. 2 as nodes 68 a, 68 b and 68 c). Generallyspeaking, the nodes of the wireless communication network 60 operate asa mesh type communication network, wherein each node receives acommunication, determines if the communication is ultimately destinedfor that node and, if not, repeats or passes the communication along toany other nodes within communication range. As is known, any node in amesh network may communicate with any other node in range to forwardcommunications within the network, and a particular communication signalmay go through multiple nodes before arriving at the desireddestination. A further conceptual example of a mesh network topology isdiscussed below with respect to FIGS. 3 and 4.

As illustrated in FIG. 2, the base node 62 includes or iscommunicatively coupled to a work station or a host computer 70 whichmay be for example any of the hosts or workstations 14 of FIG. 1. Whilethe base node 62 is illustrated as being linked to the workstation 70via a hardwired Ethernet connection 72, any other communication link maybe used instead. The base node 62 includes a wireless conversion orcommunication unit 74 and a wireless transceiver 76 to effect wirelesscommunications over the network 60. In particular, the wirelessconversion unit 74 takes signals from the workstation or host 70 andencodes these signals into a wireless communication signal which is thensent over the network 60 via the transmitter portion of the transceiver76. Conversely, the wireless conversion unit 74 decodes signals receivedvia the receiver portion of the transceiver 76 to determine if thatsignal is destined for the base node 62 and, if so, further decodes thesignal to strip off the wireless encoding to produce the original signalgenerated by the sender at a different node 64, 66 or 68 within thenetwork 60.

As will be understood, in a similar manner, each of the othercommunication nodes including the repeater nodes 64, the environmentalnodes 66 and the field nodes 68 includes a communication unit and awireless transceiver (not shown) for encoding, sending and decodingsignals sent via the wireless mesh network 60. While the different typesof nodes 64, 66, 68 within the communication network 60 differ in someimportant ways, each of these nodes generally operates to receivewireless signals, decode the signal enough to determine if the signal isdestined for that node (or a device connected to that node outside ofthe wireless communication network 60), and repeat or retransmit thesignal if the signal is not destined for that node and has notpreviously been transmitted by that node. In this manner, signals aresent from an originating node to all the nodes within wirelesscommunication range, each of the nodes in range which are not thedestination node then retransmits the signal to all of the other nodeswithin range of that node, and the process continues until the signalhas propagated to all of the nodes within range of at least one othernode. However, the repeater node 64 operates to simply repeat signalswithin the communication network 60 to thereby relay a signal from onenode through the repeater node 64 to a second node 62, 66 or 68.Basically, the function of the repeater node 64 is to act as a linkbetween two different nodes to assure that a signal is able to propagatebetween the two different nodes when these nodes are not or may not bewithin direct wireless communication range of one another. Because therepeater node 64 is not generally tied to other devices at the node, therepeater node 64 only needs to decode a received signal enough todetermine if the signal is a signal that has been previously repeated bythe repeater node (that is, a signal that was sent by the repeater nodeat a previous time and which is simply being received back at therepeater node because of the repeating function of a different node inthe communication network 60). If the repeater node has not received aparticular signal before, the repeater node 64 simply operates to repeatthis signal by retransmitting that signal via the transceiver of therepeater node 64. It should be noted, however, that repeater nodes 64may not be necessary within a wireless mesh network, provided there is asufficient number of other nodes 66, 68 in communication with oneanother to avoid isolated nodes and/or pinch points. That is, when anode must rely upon a single node or a limited number of nodes to routemessages to the base node 62, a pinch point (also known as acommunication bottleneck) may occur within the network. Repeater nodes64 may be used to alleviate pinch points or the risk of pinch points(i.e., the risk of a pinch point occurring if a node 66, 68 fails).

On the other hand, each of the field nodes 68 is generally coupled toone or more devices within the process plant environment and, generallyspeaking, is coupled to one or more devices, illustrated as fielddevices 80-85 in FIG. 2. The field devices 80-85 may be any type offield devices including, for example, four-wire devices, two-wiredevice, HART devices, Fieldbus devices, 4-20 mA devices, smart ornon-smart devices, etc., such as the devices 25-39 of FIG. 1. For thesake of illustration, the field devices 80-85 of FIG. 2 are illustratedas HART field devices, conforming to the HART communication protocol. Ofcourse, the devices 80-85 may be any type of device, such as asensor/transmitter device, a valve, a switch, etc, such as fielddevices. Additionally, the devices 80-85 may be other than traditionalfield devices such as controllers 12, I/O devices 22A-20B, work stations14, or any other types of devices. It should also be understood that afield node 68 (as well as the nodes 66) may be integrated with thedevice to which it corresponds, thereby creating a wireless device, suchas wireless controllers, wireless I/O devices, wireless workstations,wireless field devices, etc.

In any event, the field node 68 a, 68 b, 68 c includes signal linesattached to their respective field devices 80-85 to receivecommunications from and to send communications to the field devices80-85. Of course, these signal lines may be connected directly to thedevices 80-85, in this example, a HART device, or to the standard HARTcommunication lines already attached to the field devices 80-85. Ifdesired, the field devices 80-85 may be connected to other devices, suchas I/O devices 20A or 22A of FIG. 1, or to any other desired devices viahardwired communication lines in addition to being connected to thefield nodes 68 a, 68 b, 68 c. Additionally, as illustrated in FIG. 2,any particular field node 68 a, 68 b, 68 c may be connected to aplurality of field devices (as illustrated with respect to the fieldnode 68 c, which is connected to four different field devices 82-85) andeach field node 68 a, 68 b, 68 c operates to relay signals to and fromthe field devices 80-85 to which it is connected.

In order to assist in the management in the operation of thecommunication network 60, the environmental nodes 66 are used. In thiscase, the environmental nodes 66 a and 66 b includes or iscommunicatively connected to devices or sensors that measureenvironmental parameters, such as the humidity, temperature, barometricpressure, rainfall, or any other environmental parameters which mayaffect the wireless communications occurring within the communicationnetwork 60. This information may be useful in analyzing and predictingproblems within the communication network, as many disruptions inwireless communications are at least partially attributable toenvironmental conditions. If desired, the environmental sensors may beany kind of sensor and may include, for example, HARTsensors/transmitters, 4-20 mA sensors or on board sensors of any designor configuration. Of course, each environmental node 66 a, 66 b mayinclude one or more environmental sensors and different environmentalnodes may include the same or different types or kinds of environmentalsensors if so desired. Likewise, if desired, one or more of the nodes 66a, 66 b may include an electromagnetic ambient noise measurement deviceto measure the ambient electromagnetic noise level, especially at thewavelengths used by the communication network 60 to transmit signals. Ofcourse, if a spectrum other an RF spectrum is used by the communicationnetwork 60, a different type of noise measurement device may be includedin one or more of the environmental nodes 66. Still further, while theenvironmental nodes 66 of FIG. 2 are described as includingenvironmental measurement devices or sensors, any of the other nodes 68could include those measurement devices so that an analysis tool may beable to determine the environmental conditions at each node whenanalyzing the operation of the communication network 60.

It will be noted that FIG. 2 is a schematic diagram and the placement ofthe environmental nodes 66 a, 66 b relative to the field nodes 68 a-68 care not intended to be relative to their actual placement in an actualprocess control area. Rather, the environmental nodes 66 a, 66 b (andother environmental nodes not pictured or a single environmental node)are intended to be placed about the process control area in a logicaland strategic manner as shown conceptually in FIGS. 3 and 4.

FIG. 3 conceptually illustrates a network 100 with a wireless gateway102 in communication with nodes N01-N12 which correspond to variousfield devices, such as field devices 25-39, and controllers, such ascontrollers 12, where the gateway 102 and nodes N01-N12 make up awireless mesh network. The field devices and controllers to which thenodes correspond are generally considered smart-measurement,wireless-enabled process devices. Because the field devices andcontrollers are wireless-enabled process devices, they communicatewithin the network 100 and with the workstation 104 and server 106 viathe gateway 102. Thus, as with traditional hardwired network, thewireless-enabled process devices are able to exchange process data withthe workstation 104 and server 106, and in a wireless mesh orpoint-to-point configuration, each wireless-enabled field device andcontroller serves not only as a client to receive and send its own data,but also as a repeater or relay to propagate data through the network toother process devices. Thus, each wireless-enabled field device andcontroller is a node within the network 100. The term “node” as usedherein refers to a logical representation of a physical wireless-enabledprocess device within the network 100. Accordingly, it should beunderstood that while the term “node” is used to describe themaintenance route generation techniques, the term is also representativeof the wireless process devices that physically make up the network 100.Thus, the maintenance route generation techniques, although describedherein with reference to nodes, may be performed using identification ofprocess devices, such as device tags or other identification thatuniquely identifies each process device within the network 100.

The wireless gateway 102 and nodes N01-N12 communicate using a wirelesscommunication protocol, such as WirelessHART protocol (IEC 62591),although other wireless protocols may also be used. WirelessHARTprotocol is a time division multiple access (TDMA) channel access andchannel hopping for communication within wireless network 100. Networkmanager software may be implemented on the wireless gateway 102 in orderto schedule communications among nodes N01-N12 and the wireless gateway102, and define communication paths within the wireless mesh network100. Although FIG. 3 shows wireless mesh network 100 with only a singlegateway 102, more than one gateway may be provided, in which case thegateways may share network manager software. Likewise, although only 12nodes are shown, a mesh network can easily have dozens or hundreds ofnodes making up the network, which makes the maintenance routegeneration routine all the most useful.

The mesh network 100 is, in turn, connected to host workstations orcomputers 104, such as the host workstations or computers 14, and/orservers 106 via a communication link 108, illustrated as an Ethernetconnection, such as the Ethernet connection 40. The gateway 102 maycorrespond to the base node 62 above, and interfaces the mesh networkwith the host workstations 14 and/or servers 106 via the Ethernetconnection 108 using a number of different protocols, such as thosementioned above. As such, while the wireless gateway 102 is illustratedas being linked to the workstation 104 via the hardwired Ethernetconnection 108, any other communication link may be used instead, suchas a wireless communication link, examples of which were provided above.

Where the wireless mesh connections are shown in broken line, optionallysome or all of the nodes N01-N12 may be connected in a wirelesspoint-to-point configuration, as shown by the solid lines in FIG. 3.Thus, it should be understood that the network 100 may have alternativeconfigurations, such that the network 100 may be solely a wirelesspoint-to-point network, solely a wireless mesh network, switchable froma wireless point-to-point network to a wireless mesh network and viceversa, or a combination of wireless point-to-point and wireless meshnetworks. Examples of switchable wireless networks (e.g., mesh topoint-to-point and vice versa) and combination of wirelesspoint-to-point and wireless mesh networks disclosed in Shepard et al.,U.S. Pat. No. 7,436,797 referenced above. It should further beunderstood that the network 100 may be implemented in combination with ahardwired network, such as that disclosed in Chen et al., U.S. Pat. No.7,822,802 entitled “Apparatus and Method for Merging Wireless Data IntoAn Established Process Control System” and patented Oct. 26, 2010, thecontent of which is expressly incorporated by reference herein.

Although not necessarily representative of the placement of the nodesN01-N12 relative to their actual placement in an actual process controlarea, FIG. 3 does conceptually represent the placement of the nodesN01-N12 relative to one another and relative to the wireless gateway102. For example, in a wireless mesh network relative to the wirelessgateway 102, node N03 is closest, node N01 is the next closest and thenode N02 is the furthest from the wireless gateway 102. Relative to nodeN01, node 04 is the closest, node N02 is the next closest, node N06 isthe next closest thereafter and node 05 is the furthest from the nodeN01, and so on and so forth with every node in the network 100. Note,only those nodes that are in direct communication are considered asbeing relative to one another. For example, in a point-to-point wirelessnetwork the placement of the network nodes N01, N02 and N03 would beconsidered relative to the wireless gateway 102, but not relative toeach other because node N01-N03 do not communicate directly with oneanother. Likewise, in a hardwired network the placement of the networknodes N01, N02 and N03 would be considered relative to the Ethernet 104,but not relative to each other.

The zero hop counts for the wireless mesh network shown in FIG. 3 areshown in tabular form in FIG. 4A, and the zero hop counts for thewireless point-to-point network are shown in tabular form in FIG. 4B.The listing of nodes (and the gateway, where applicable) in the rows isarranged according to the physical distance of the node from the node(or gateway) listed in the first column. However, it is not necessarilyindicative of the route of messages through the network, particularlywith respect to a mesh network where a data packet may take any of anumber of routes to its destination.

Referring to FIG. 4A, the wireless gateway 102 communicates directlywith nodes N01 through N03 and therefore the hop count between thewireless gateway 102 and any one of N01 through N03 is zero. Turning tothe second row of the table of FIG. 4A, it will be noted that the hopcount between node N01 and nodes N02 and N04-N06 is also zero as nodeN01 is illustrated in FIG. 3 as having direct communication with thegateway 102 and each of nodes N02 and N04-N06. Likewise, each of theremaining rows of the table in FIG. 4A demonstrate the zero hop countsfor each of the nodes N02-N12.

Referring to FIG. 4B, the wireless gateway 102 communicates directlywith nodes N01 through N03, such that the hop count between the wirelessgateway 102 and any one of N01 through N03 is again zero. In the secondrow of the table of FIG. 4B, however, the hop count between node N01 andthe other nodes is zero with respect to only N04-N06 and the gateway 102as node N01 is illustrated in FIG. 3 as only having direct communicationwith the gateway 102 and each of nodes N04-N06, but not node N02 in thisinstance. Again, each of the remaining rows of the table in FIG. 4Bdemonstrate the zero hop counts for each of the nodes N02-N12 in apoint-to-point wireless network.

As field devices and controllers are implemented within a processcontrol system, nodes are added to the network, be it a wireless meshnetwork or a wireless point-to-point network. Likewise, field devicesand controllers may be taken offline or removed from the process controlsystem, thus removing nodes from the network. As nodes are added orremoved from a network, the communication paths may change. Accordingly,the gateway 102, workstation 104 and/or server 106 may periodicallygather information about the network using various diagnostic tools inorder to identify, define and/or update the communication paths/routestherein.

As is known, the gateway 102 may collect information about the network100, including information about each node N01-N12. For example, asmentioned above with respect to a wireless mesh network 100, networkmanager software may be used to schedule communications and definecommunication paths within the network 100. In particular, the networkmanager defines communication paths for messages transmitted from thegateway 102 to the various nodes N01-N12, and vice versa. Thecommunication paths are assigned by network manager using informationreceived from each of the nodes N01-N12. As each node is introduced intothe network, the node communicated with other nodes within range todetermine its neighbors (i.e., other nodes or the gateway in directactive communication with the node). Each node measures the receivedsignal strength, referred to as the received signal strength indicator(RSSI) which is a measure of the power of a received signal, during eachcommunication with a neighbor, among other statistics regardingcommunications with its neighbors.

Information about each node's neighbors and corresponding RSSI may betransmitted to the gateway 102 and used by the network manager software.For example, the network manager software may use the neighborinformation and RSSI information to determine the communication pathsfor incoming and outgoing messages. For each communication path, thenetwork manager software identifies the neighboring nodes for thevarious hops in the path. The nodes within a communication path may beclassified as a parent or a child, where a parent is a device thatpasses communications through itself for another device (its child), anda child is a device that communicates through another device (a parent)to reach a third device or gateway.

Each of nodes N01-N12 periodically reports its communication statisticsto the gateway 102. These statistics are used by the network managersoftware to determine communication paths and assign time slots formessages. The communication statistics may include identification ofneighbors, received signal strength indicators (RSSI) from eachneighbor, received signal strength indicators (RSSI) to each neighbor,the percentage of successful communications with each neighbor, numberof parents and children to that particular node, parent-to-childrenratio, parent-to-neighbor ratio, and children-to-neighbor ratio, whetherthe node is within range of gateway 102, and whether the node is indirect communication with the gateway 102. Thus, using diagnostic tools,such as the network manager software, the communication paths within amesh network may be determined.

For point-to-point wireless networks, each node is capable of collectingand transmitting communication statistics to the gateway 102, in whichcase the gateway 102 in a point-to-point network may be implemented withnetwork manager software stored thereon. The network manager softwarereceives from each node communication statistics including receivedsignal strength indicators (RSSI) from each neighbor, received signalstrength indicators (RSSI) to each neighbor, the percentage ofsuccessful communications with each neighbor, etc. Thus, in apoint-to-point network, the communication path may likewise bedetermined using a diagnostic tool, such as the network managersoftware.

A further commonly used diagnostic tool is a tracing tool such astraceroute, which determines the route of communications in the networkand measures transit delays of messages across the network. As isgenerally known, traceroute sends a sequence of echo request packetsaddressed to a destination node. Traceroute determines the intermediatenodes traversed in the communication path by adjusting time-to-live(TTL) (hop limit) network parameters. The TTL (hop limit) value isdecremented at each node in the communication path, a packet discardedwhen the TTL value has reached zero, and an error message returned tothe message origin indicating time exceeded. The TTL value (hop limit)is increased for each successive set of packets sent, where a first setof packets have a hop limit value of 1 with the expectation that theyare not forwarded on by the first node. The first node then returns theerror message back to the origin. The next set of packets have a hoplimit value of 2, so that they are not forwarded beyond the second nodein the communication path, and the second node sends the error reply.This continues until the destination node receives the packets andreturns an echo reply message. Traceroute uses the returned messages toproduce a list of nodes that the packets have traversed. The timestampvalues returned for each node along the path are the delay (latency)values, typically measured in milliseconds. Thus, the number of hops andlatency values may be determined for the network, and, in turn, thecommunication path may be determined for the network.

Referring now to FIG. 5, a maintenance route generation routine 200 forestablishing maintenance routes through the process plant is disclosed.The maintenance route generation routine 200 utilizes information fromthe above-described diagnostic utilities, such as signal strength, hopcount and latency, to automatically create and modify the maintenanceroutes. Generally, the routine 200 of FIG. 5 is executed on the back endof the Ethernet 108, such as on the workstation 104 or the server 106,for example. More specifically, the maintenance route generation routine200 is implemented and executed as a tool on a maintenance computer.That is, a computer, such as a workstation 104 or server 106, designatedfor maintenance related activities and/or which executes an interfaceapplication to enable a maintenance person to interface with the processcontrol network 10 within the plant. In one example, the maintenanceroute generation routine 200 may be implemented as a module of theinterface application.

The process by which a maintenance route is established is based on asequence of calculations relating to relative proximity that is derivedfrom the signal strength and number of hops that occur in thecommunication path for a given set of field devices and controllers(nodes). That is, the proximity of nodes with respect to one another canbe gleaned from the information about the network without having to knowthe physical location of each device. For example, referring to FIGS. 3and 4, even if the actual distance between 1) node N01 and 2) nodes N02,N04, N05 and N06 is not known, it may nonetheless be determined fromsignal strength that node N04 is the closest to node N01 (i.e., node N04has greater RSSI than nodes N05 or N06). Thus, while distance may not bedetermined from signal strength, it can provide an indication of whichnode is closest relative to another node, and hence which field deviceor controller is closest relative to another field device or controller.

It should be understood that a defined maintenance route does notstrictly follow a communication path through the network 100. Oftentimes there are many reasons why a communication route and maintenanceroute will differ. Where a maintenance route is established based on therelative physical proximity of nodes, communication routes may bepartially based on proximity by virtue of a node's communication range(for example, the radio range of a wireless device) and based on logicalcommunication parameters, such as avoiding pinch points. Nonetheless,the information used to determine communication routes is useful indetermining maintenance routes. Further, while the following descriptionrelates to nodes within the network 100, it should readily be understoodthat field devices and controllers are the physical embodiments of thenodes, and that the term “nodes” may just as easily be substituted withthe terms “field devices” and “controllers” within this context, wherethe field devices and controllers are implemented as wireless enabledfield devices and controllers.

Referring to FIG. 5, a comprehensive list (List A) of all field devicesand controllers communicating with the gateway, either directly orindirectly, is created at block 202 (see FIG. 6A). Generally speaking,the gateway 102 and the network manager software maintain a list of allnodes (and thus all field devices and controllers) in communication withthe gateway 102, in order to identify, define and/or update thecommunication paths/routes therein. In addition or in the alternative,these lists may likewise be maintained by the workstation 104 and/orserver 106. Accordingly, creating a list of all field devices andcontrollers communicating with the gateway 102 may be accomplished byretrieving the list of nodes N01-N12 created and maintained by thegateway 102 as part of its regular network diagnostics. At a minimum,existing information about the network 100 may be taken from the gateway102 to create a list of all nodes N01-N12 within the network.

Once a list of all nodes communicating with the gateway is created, aprimary ordered list (List B) is created at block 204 of all devices indirect communication with the gateway using the nodes listed in List A(see FIG. 6B). Using the results from the network diagnostics, the hopcount of each node is known, as is the RSSI (or other indicator ofsignal strength) for each device relative to its neighbors.Specifically, List B is an ordered list of all nodes with 0 hops intheir communication path arranged by signal strength. Referring to FIGS.3 and 4, this would be nodes N03, N01 and N02 in that order, as each hasa zero hop count with respect to the gateway 102, and of these the RSSIof N03 is strongest relative to the gateway 102, N01 is the nextstrongest and N02 is the weakest.

FIG. 7 is a flowchart of an example of a routine 204 for creating anordered list (List B) of nodes in direct communication with the gateway102 (i.e., nodes with 0 hop from gateway 102). Using List A created atblock 202 of FIG. 5, the routine 204 of FIG. 7 selects those nodes with0 hop from the gateway 102 and ranks the nodes in List B according to asignal strength of the wireless connection between each node in List Band the wireless gateway network device, with higher signal strengthsranked ahead of weaker signal strengths. Referring to FIG. 7, the firstnode in List A (e.g., node N01) may be selected at block 302 with adetermination being made at block 304 as to whether the selected node isin direct communication with the gateway 102 (i.e., is the hop for thenode zero?). If not, the routine 204 moves on to the next node in List Aand repeats the same determination at block 304.

If the node hop is zero with respect to the gateway 102, the node isadded to the bottom of List B at block 308. If this is the first nodeadded to List B, such a determination is made at block 310, whereby theroutine 204 then selects the next node from List A at block 306. If thisis a second or subsequent 0 hop node being added to List B, the routine204 then proceeds to order the list according to signal strength withthe gateway 102 at block 312.

In ordering the list according to signal strength, the signal strengthof the added node (with the exception of the first node added to thelist) is compared to the signal strength of the immediately precedingnode listed in List B at block 312. This is performed with respect toeach node in List B until the added node is ranked below a node having ahigher signal strength. In particular, if the signal strength of theadded node is higher than that of the node listed above it, the addednode is moved up on spot in List B ahead of the node with the lowersignal strength at block 314. The signal strength of the added node isthen compared to the signal strength of the next node in the list,namely the node, if any, that now immediately precedes the added nodeafter it was moved up one spot in the list. Again, if the signalstrength of the added node is higher than that of the node now listedabove it, the added node is moved up on spot in List B ahead of the nodewith the lower signal strength at block 314. This process continuesuntil it is determined at block 312 that the added node does not have asignal strength stronger than that listed above it, at which point thenext node from List A is selected at block 306, unless it is determinedat block 316 that the end of List A has been reached, in which casecontrol is returned to the maintenance route generation routine 200 ofFIG. 5.

The result from the routine 204 of FIG. 7 is List B, which is a listingof nodes in direct communication with the gateway 102. For example,referring to FIGS. 3, 4 and 6A, the nodes in direct communication withthe gateway 102 are node N01, N02 and N03. Using the routine 204 of FIG.7, the first node selected by the routine 204 is node N01, where it isdetermined that node N01 has a zero hop count with respect to thegateway 102. Being the first node added to List B, the routine 204proceeds to select the next node from List A, namely node N02. Havingdetermined that node N02 has a zero hop count with respect to thegateway 102, node N02 is added to the end of List B, and the signalstrength of node N02 with the gateway 102 is compared to that of nodeN01. Then, having determined that the signal strength of node N02 isless than that of node N01, the routine 204 selects the next node fromList A, namely node N03. Node 03, having a zero hop count with thegateway 102, is added to the end of List B. The signal strength of nodeN03 is compared to that of node N02, whereby it is determined that nodeN03 has a stronger signal with the gateway 102 than node N02, so it ismoved ahead of node N02 in List B. Subsequently, it is determined thatthe node N03 also has a strong signal than that of node 01, so node N03is move to ahead of node N01 in the list. Each of nodes N04-N12 are thenselected from List A, but each is determined to have a hop count of 1 orgreater with respect to the gateway 102. What results is an ordered listof nodes in direct communication with the gateway 102 and arrangedaccording to signal strength, namely N03, N01, N02 as shown in FIG. 6B.While the routine 204 is useful in creating this ordered list of nodes,it should be understood that the routine of FIG. 7 is but one example ofcreating an ordered list of nodes in direct communication with thegateway 102 arranged according to signal strength, and that otherroutines may be utilized.

Referring back to FIG. 5, the process of creating secondary orderedlists (List C) of nodes arranged according to signal strength isiteratively repeated for each node in direct communication with nodes inList B and arranged by signal strength. That is, for each node in List Bcreated at block 204, the process is repeated for any node communicatingdirectly with the node in List B. In particular, the first node listedin List B (i.e., node N03) is selected at block 206 of FIG. 5. Fromthere, all nodes with 0 hops in their communication path with respect tonode N03 (i.e., neighbors of node N03) are selected from List A andarranged by signal strength in List C. Referring to FIGS. 3, 4 and 6C,this would be nodes N11, N10 and N02 in that order, as each has a zerohop count with respect to node N03, and of these the RSSI of N11 isstrongest relative to node N03, N10 is the next strongest and N02 is theweakest.

FIG. 8 is a flowchart of an example of a routine 208 for creating anordered list (List C) of nodes in direct communication with a node fromList B (i.e., nodes with 0 hop from the selected node of List B). Aswill be seen, FIG. 8 is first discussed with respect to the first nodefrom List B (node N03), and thereafter explained with respect to theother nodes in List B. Using List A created at block 202 of FIG. 5, theroutine 208 of FIG. 7 selects those nodes with 0 hop from node N03 andranks the nodes in List C according to a signal strength of the wirelessconnection between each node in List C and node N03, with higher signalstrengths ranked ahead of weaker signal strengths. Referring to FIG. 8,the first node in List A (e.g., node N01) may be selected at block 402with a determination being made at block 404 as to whether the selectednode is in direct communication with node N03. If not, the routine 208moves on to the next node in List A (e.g., node N02) and repeats thesame determination at block 404.

If the node hop is zero with respect to node N03, the node is added tothe bottom of List C at block 408. If this is the first node added toList C, such a determination is made at block 410, whereby the routine208 then selects the next node from List A at block 406. If this is asecond or subsequent 0 hop node being added to List C, the routine 208then proceeds to order the list according to signal strength with nodeN03 at block 412. In this iteration, nodes N02, N10 and N11 are deemedto be in direct communication with node 03.

In ordering the list according to signal strength, the signal strengthof the added node (with the exception of the first node added to thelist) is compared to the signal strength of the immediately precedingnode listed in List C at block 412. This is performed with respect toeach node in List C until the added node is ranked below a node having ahigher signal strength. In particular, if the signal strength of theadded node is higher than that of the node listed above it, the addednode is moved up on spot in List C ahead of the node with the lowersignal strength at block 414. For example, in this iteration node N02 isthe first node added to List C, as it is the first one selected fromList A having a 0 hop count with respect to node N03. N10 is the nextnode added to List C.

The signal strength of the added node is then compared to the signalstrength of the next node in the list, namely the node, if any, that nowimmediately precedes the added node after it was moved up one spot inthe list. Again, if the signal strength of the added node is higher thanthat of the node now listed above it, the added node is moved up on spotin List C ahead of the node with the lower signal strength at block 414.For example, the signal strength of node N10 with respect to node N03 iscompared to that of node N02, whereby it is determined that node N10 hasthe stronger signal and is moved ahead of node N02 in List C. Thus, ListC is N10, N02 in that order. This process continues until it isdetermined at block 412 that the added node does not have a signalstrength stronger than that listed above it, at which point the nextnode from List A is selected at block 406, unless it is determined atblock 416 that the end of List A has been reached, in which case controlis returned to the maintenance route generation routine 200 of FIG. 5.For example, node N11 is the next node selected from List A as being indirect communication with node N03 from List B. Node 11 is added to theend of List C, and its signal strength is compared to that of N02 (i.e.,the immediately preceding node in List C). Node N11 has a strong signalthan that of node N02, so it is moved ahead of node N02. The signalstrength comparison is then performed between nodes N11 and N10, wherebynode N11 is moved up to the top of List C ahead of node N10. The resultfrom the routine 208 of FIG. 8 is List C, which is a listing of nodes indirect communication with node N03 and arranged according to signalstrength with node N03, namely N11, N10 and N02 as shown in FIG. 6C.While the routine 208 is useful in creating this ordered list of nodes,it should be understood that the routine of FIG. 8 is but one example ofcreating an ordered list of nodes in direct communication with nodesfrom List B arranged according to signal strength, and that otherroutines may be utilized.

Referring back to FIG. 5, the ordered list of nodes in List C isappended to List B at block 210 after the node of List B for which thenodes of List C are in direct communication. For instance, continuingwith the above example, the list of nodes N11, N10 and N02 is appendedto List B after node N03, as shown in FIG. 6D. More specifically, nodesN11 and N10 are appended to List B after node N03, and node N02 is movedup in List B ahead of node N01, despite the earlier arrangement of nodeN01 ahead of node N02 (see FIG. 6B). This is because node N02 is alreadylisted in List B.

FIG. 9 depicts a routine 210 for appending List B with List C after thenode selected from List B. For the above example, this begins with thefirst node in List B as selected at block 206 of FIG. 5, namely nodeN03, but, as will be explain further, applies to all nodes subsequentlyselected from List B at block 214 of FIG. 5. Referring to FIG. 9, thefirst node from List C is selected by the routine at block 502, which,in the present example, is node N11. In order to avoid listing nodesmultiple times (as would be the case with node N02 as it already existsin List B), the routine 210 proceeds to add nodes from List C andreorder the nodes in List B as needed to provide the most efficientphysical maintenance route among the nodes. As such, at block 504 theroutine 210 determines whether the node selected from List C is alreadylisted above the node from List B selected in the maintenance routegeneration routine 200 of FIG. 5. If so, the node from List C isdiscarded or otherwise not appended to List B, and the routine 210proceeds to select the next node from List C at block 506 and repeat thedetermination at block 504.

If the node selected from List C is not listed above the node selectedfrom List B, then the routine determines whether the node selected fromList C is already listed in List B at block 508 (as would be the casefor node N02). If the node is already listed in List B, the node ismoved up in the list in accordance with the order of nodes according toList C at block 510. Otherwise, the node is appended from List C to ListB according to the order of nodes in List C at block 512. This processis repeated for each node in List C until then end of List C is reachedas determined at block 514.

In the context of the example having been discussed herein, the routine210 would first select node N11 from List C. As node N11 is not alreadylisted above node N03 (the node selected from List B during themaintenance route generation routine 200 of FIG. 5), and is not alreadylisted in List B, node N11 is added to List B after node N03. The nextnode in List C, node N10, is also not already listed above node N03 andnot listed in List B, so it is added after node N11 in accordance withthe order of List C. The last node selected from List C, node N02, isnot already listed above node N03, but is already listed in List B. Assuch, it is moved up in List B in accordance with the order of List C,namely after node N10. Thus, using signal strength as an indicator, ListB, in order of proximity, results in starting at node N03, andproceeding in order to nodes N11, N10, N02 and N01 as shown in FIG. 6D.

As previously mentioned, the process of creating ordered lists (List C)of nodes arranged according to signal strength is iteratively repeatedfor each node in direct communication with nodes in List B and arrangedby signal strength. As each node in List B is selected and List Bappended with neighboring nodes in direct communication with the nodeselected from List B, the selected node from List B may be consideredexhausted from List A. That is, it need not be considered in furtheriterations of appending List B (as indicated by the hashed outline ofnode N03 in FIG. 6C). Thus, once all nodes from List A have beenexhausted, List A is considered exhausted at block 212. Otherwise, themaintenance route generation routine 200 of FIG. 5 proceeds to selectthe next node from List B at block 214, which in the above example wouldnow be node N11, and repeats the process of creating an ordered List Cof nodes from List A in direct communication with the node selected fromList B and arranged according to signal strength with the node selectedfrom List B. The nodes of List C are again appended to List B asexplained above until all nodes have been exhausted. As an alternativeto exhausting List A, the maintenance route generation routine 200 ofFIG. 5 may otherwise track the list of nodes in List B until itdetermines that no further node may be appended to List B.

Continuing with the above example, node N11 is selected at block 214,and neighboring nodes of node N11 are arranged according to signalstrength at block 208. This results in a List C of N10 and N03. Whenappended to List B at block 210, node N10 is already listed in List Bimmediately after node N11, so it is not moved up any further. Node N03is already listed above node N11, so it is not moved. The resultingappended List B is then N03, N11, N10, N02, N01.

The next node in List B is then N10, which has a List C of neighboringnodes N11, N08, N03, N02 and N12 in order of signal strength. Whenappended to List B, node N11 is already ranked ahead of node N10, so itis not moved. Node N08 is neither ranked ahead of node N11 nor listed inList B, so it is added to List B after node N10. Node N03 is alreadyranked ahead of node N10 in List B, so it is not moved. Node N02 isalready listed in List B and is kept in place after node N08 inaccordance with the order of List C for selected node N10. Node N12 isthen added after node N02 also in accordance with the order of List Cfor selected node N10. The resulting appended List B is then N03, N11,N10, N08, N02, N12, N01.

In the next iteration, the next node in List B is Node 08 which has aList C of neighboring nodes N02, N07, N10 and N09 in order of signalstrength. When appended to List B, node N02 is already listed in List Band is kept in place after node N08 in accordance with the order of ListC for selected node N08. Node N07 is added to List B after Node 02 alsoin accordance with the order of List C, node N10 is already ranked aheadof node N08 so it is kept in place, and node N09 is added to List Bafter node N07 in accordance with the order of List C. The resultingappended List B is then N03, N11, N10, N08, N02, N07, N09, N12, N01.

In the following iteration, the next node in List B is Node 02 which hasa List C of neighboring nodes N08, N01, N10, N07, N03 in order of signalstrength. When appended to List B, node N08 is already listed ahead ofnode N02 in List B and is kept in place. Node N01 is already listed inList B, and is moved up after Node N02 in accordance with the order ofList C. Node N10 is already ranked ahead of node N02 so it is kept inplace. Node 07 is already listed in List B and remains listed after nodeN01 in accordance with the order of List C. Node N03 is already rankedahead of node N02 so it is kept in place. The resulting appended List Bis then N03, N11, N10, N08, N02, N01, N07, N09, N12.

In the subsequent iteration, the next node in List B is Node 01 whichhas a List C of neighboring nodes N04, N02, N06, N05 in order of signalstrength. Node N04 is added to List B after Node 01 in accordance withthe order of List C. Node 02 is already ranked ahead of node N01 in ListB. Nodes N06 and N05 are added to List B after Node N04 in accordancewith the order of List C. The resulting appended List B is then N03,N11, N10, N08, N02, N01, N04, N06, N05, N07, N09, N12.

The next node in List B is Node 04 which has a List C of neighboringnodes N05, N01 and N06 in order of signal strength. Each of nodes N05,N01 and N06 are already listed in List B, with node N01 already beingranked ahead of node N04. Node N05 is moved ahead of node N06 based onthe order of List C. The resulting appended List B is then N03, N11,N10, N08, N02, N01, N04, N05, N06, N07, N09, N12.

Subsequent iterations do not result in any further changed to appendedList B thereafter. Accordingly, as the maintenance route generationroutine 200 of FIG. 5 proceeds through the remaining iterations fornodes N05, N06, N07, N09 and N12, List A is exhausted and the final ListB is as follows: N03, N11, N10, N08, N02, N01, N04, N05, N06, N07, N09,N12 as shown in FIG. 6E. This final List B is then outputted as what isconsidered to be the most efficient maintenance route among the nodes,and hence among the field devices and controllers associated with eachnode, where the order of the nodes in List B is the order of themaintenance route and the location of each corresponding field device orcontroller corresponds to a stop point in the route. Thus, using networkdiagnostic information such as hop counts to identify neighboring nodesand the signal strength of the neighboring nodes as an indicator ofproximity, a maintenance route may be generated for maintenancepersonnel to physically walk through the process plant to performvarious maintenance and calibration activities as defined by themaintenance route.

Various modifications and/or utilizations may be made with themaintenance route. For example, while the maintenance route generationroutine 200 of FIG. 5 may be considered the most optimal route throughthe process plant (or at least through the field devices and controllerof the network 100), maintenance personnel may modify the route asneeded, for example based on certain field devices or controllersneeding quicker maintenance than others. In other example, themaintenance route may be modified to remove nodes that correspond withfield devices and/or controllers that do not require maintenance orcalibration.

At a minimum, the maintenance route may be displayed over on a map ofthe process plant on a display screen, such as a display screen of theworkstation 104 or on a handheld device having a display screen, such asa smartphone, tablet pc, personal digital assistant or other portabledisplay device. In particular, where each node is associated with afield device or controller and the location of the field device orcontroller is known, the field devices and controllers may be shown on amap of the process plant. For example, Citrano, III, U.S. PatentApplication Publication No. 2009/0265635 entitled “System ForVisualizing Design and Organization of Wireless Mesh Networks InPhysical Space,” filed Feb. 27, 2009 and published Oct. 22, 2009, thecontent of which is expressly incorporated by reference herein,discloses a visualization tool that display devices included in a meshnetwork with respect to the physical space occupied by the network. Thetool receives an image representing the physical space occupied by thewireless mesh network, scale information defining the scale of thereceived image, and location information defining the location of eachdevice within the physical space occupied by the network. Based on theseinputs, the visualization tool displays the layout of the wireless meshnetwork with respect to the physical space occupied by the wireless meshnetwork. Using this tool, the maintenance route generated by themaintenance route generation routine 200 may be overlaid on the displayof the layout of the mesh network, with arrows indicating the orderedroute from node to node, and hence device to device, as conceptuallyshown in FIG. 10.

Further, maintenance routes generated by the maintenance routegeneration routine 200 may be updated on the basis of field devices orcontrollers (and hence nodes) being added or removed from the network100. For example, having established a maintenance route, a new node N13may be added to the network 100 having neighbors N08, N10, N12 and N09as its neighbors in order of signal strength. Rather than repeat theprocess for each of the nodes within the network, which can number inthe dozens or hundreds, the process may be executed with just the newnode and its neighbors. That is, having neighbors N08, N10, N12 and N09,List A may be created with nodes N08, N09, N10, N12 and N13. Having analready established maintenance route as defined by List B from above,blocks 202-206 may be skipped, as these are essentially forinitialization of List B.

As should be understood, the introduction of a new node into the network100 may change the optimal route for maintenance, as the new node N13may be now closer to existing nodes than previous neighbors. Forexample, node N13 may now be the closest neighbor of node N08, wherepreviously node 02 was the closest neighbor to N08 Likewise, node N13may now be the second closest neighbor of node N10, where previouslynode N08 was the second closest neighbor. In order to arrange the nodesin optimal order for a maintenance route based on proximity, the processis repeated for each node in List B that communicates directly with newNode N13, namely nodes N08, N09, N10 and N12. Thus, beginning with nodeN10 (as node N10 is the first listed in List B among nodes N08, N09, N10and N12 n (see FIG. 6E)), a List C may be created of all of node N10'sneighbors in order of signal strength, which now includes new node N13(e.g., N11, N13, N08, N03, N02, N12). The List C may then be appended toList B as disclosed above, thereby introducing new node N13 to List B.The process is then repeated for nodes N08, N09, N10 and N12 and alsofor node N13, to finalize List B and establish a modified maintenanceroute.

Should a field device or controller (and hence node) be removed from thenetwork 100, the node may be removed from List B, and a similar processmay be carried out for those nodes that were neighbors of the removednode. Thus, without having to execute the maintenance route generationroutine 200 for all nodes in the network 100, an existing maintenanceroute may be modified to account only for those nodes affected by theintroduction or removal of another node.

While the above example has been described with respect to the wirelessmesh network of FIG. 3 as indicated by the broken communication lines,the maintenance route generation routine 200 is likewise applicable towireless point-to-point wireless networks, such as that shown by thesolid communication lines in FIG. 3. For example, using the maintenanceroute generation routine 200, List A is created at block 202 (FIG. 11A),similar to that shown in FIG. 6A. Using the routine of FIG. 7 forcreating an ordered list (List B) of nodes in direct communication withthe gateway 102 at block 204, an ordered List B (FIG. 11B) is created ofnodes with a 0 hop count from the gateway 102 (i.e., nodes N03, N01,N02) and arranged in order of signal strength with the gateway 102,similar to that shown in FIG. 6B.

Selecting the first node from List B (i.e., node N03) at block 206, themaintenance route generation routine 200 then creates an ordered List C(FIG. 11C) of nodes with a 0 hop count from the selected node from ListB (i.e., node N03) and arranged in order of signal strength with theselected node from List B at block 208 using the routine of FIG. 8 forcreating an ordered list (List C) of nodes in direct communication witha node from List B. However, unlike the List C for selected node N03from List B in the example of the mesh wireless network above (see FIG.6C), the list does not include node N02, because in the point-to-pointnetwork example of FIG. 3 only node N10 and N11 are neighbors with nodeN03. Thus, List C for selected node N03 includes nodes N11 and N10 inorder of signal strength.

At block 210, List C for selected node N03 is appended to List Baccording to the routine 210 for appending List B with List C after thenode selected from List B, resulting in the List B of FIG. 11D. Node N02remains in List B from the initial creation of ordered List B, butcontrasted with FIG. 6D, it remains ranked behind Node 01. Thereafter,the maintenance route generation routine 200 determines whether eachnode has been accounted for at block 212, and selects the next node fromList B at block 214 if needed.

Continuing with the present example, once List B has been appended forselected node N03, the next node in appended List B is now node N11,which has only one neighbor, node N03. Given that node N03 is alreadylisted ahead of node N11, the routine 200 moves on to node N10 withoutappending List B after going through the steps of routines 208 and 210.The next node in List B is now node N10, which has neighboring nodes N03and N12. Using the process of FIG. 8 at block 208, List C for selectednode N10 from List B results in nodes N03 and N12 in order of signalstrength. Using the process of FIG. 9 at block 210, List C is appendedto List B after node N10, where node N03 is already ranked ahead of nodeN10 and node N12 is ranked below node N10. The resulting appendedordered List B is then nodes N03, N11, N10, N12, N01, N02.

As with the mesh network example above, the maintenance route generationroutine 200 repeats blocks 208, 210, 212 and 214 for the nodes in awireless point-to-point network. However, the resulting ordered listsare different than for a wireless mesh network. For example, once List Bhas been appended for selected node N10, the next node in List B is nodeN12, which has only one neighbor, node N10. Given that node N10 isalready listed ahead of node N12, the routine 200 moves on to node N01without appending List B after going through the steps of routines 208and 210. At this point, node N01 is selected from List B, which hasneighbors N04, N05 and N06, resulting in an ordered List C of nodes N04,N06, N05 and an appended List B of N03, N11, N10, N12, N01, N04, N06,N05, N02. Because each of nodes N04, N05 and N06 only have node N01 as aneighbor, and because node N01 is already ranked ahead of these nodes inordered List B, the resulting iterations for nodes N04, N06, N05 (asthey are selected in order from List B) do not result in any changes toordered List B). Thereafter, node N02 is selected resulting in nodes N08and N07 being appended to List B, in that order. In the followingiteration, node N09 is appended to List B after node N08. Node N07 hasno neighbors that are not already ranked ahead of it in List B. Thus,List A is exhausted, resulting in a final List B of nodes N03, N11, N10,N12, N01, N04, N06, N05, N02, N08, N09, N07 as shown in FIG. 11E.

As above, this List B is outputted as the order of the maintenance routefor devices corresponding to the nodes. The list may be updated toaccount for nodes added or removed from the wireless point-to-pointnetwork as described above for the wireless mesh network, and may beoverlaid on a display of the layout of the wireless point-to-pointnetwork, with arrows indicating the ordered route from node to node, andhence device to device, as shown in FIG. 12. It is noted, however, thatthis may not represent the most optimum route through the network.

In particular, compared to the route shown in FIG. 10, which isconsidered a more optimum route, if not the most optimum route, theroute shown in FIG. 12 may be considered less optimal in terms ofdistance to be traversed by a maintenance person, even though the nodes(and devices) are physically positioned the same in both instances. Forexample, the leg from node N12 to node N01 bypasses node N02. Moreover,the leg from node N05 to node N02 crosses over the leg from node N04 tonode N06. In short, the route outputted by the maintenance routegeneration routine 200 for a wireless point-to-point network may not bethe most optimum route. Thus, just as maintenance personnel may modifythe route based on certain field devices or controllers needing quickermaintenance than others or to remove nodes that correspond with fielddevices and/or controllers that do not require maintenance orcalibration, the route outputted by the maintenance route generationroutine 200 for a wireless point-to-point network may be reviewed andadjusted by maintenance personnel to account for more optimal paths.Nonetheless, whereas previously maintenance routes were generatedmanually, the maintenance route generation routine 200 may, at aminimum, automatically generate a maintenance route for either wirelessmesh networks or point-to-point networks, or a combination thereof, thatmay be used as an initial list of ordered stop points for maintenancepersonnel to use for physically walking through a plant and performtasks, such as gathering data, calibrating device, performing visualequipment inspection, etc.

Although the forgoing text sets forth a detailed description of numerousdifferent embodiments of the invention, it should be understood that thescope of the invention is defined by the words of the claims set forthat the end of this patent. The detailed description is to be construedas exemplary only and does not describe every possibly embodiment of theinvention because describing every possible embodiment would beimpractical, if not impossible. Numerous alternative embodiments couldbe implemented, using either current technology or technology developedafter the filing date of this patent, which would still fall within thescope of the claims defining the invention.

While the maintenance route generation technique, and its elements, hasbeen described as routines that may be implemented on a workstation orserver, they may also be implemented in hardware, firmware, etc., andmay be implemented by any other processor, including multipleprocessors. Thus, the elements described herein may be implemented in astandard multi-purpose CPU or on specifically designed hardware orfirmware such as an application-specific integrated circuit (ASIC) orother hard-wired device as desired. When implemented in software, thesoftware routine may be stored in any computer readable memory such ason a magnetic disk, a laser disk, or other storage medium, in a RAM orROM of a computer or processor, in any database, etc.

Thus, many modifications and variations may be made in the techniquesand structures described and illustrated herein without departing fromthe spirit and scope of the present invention. Accordingly, it should beunderstood that the methods and apparatus described herein areillustrative only and are not limiting upon the scope of the invention.

What is claimed is:
 1. A method of automatically generating an orderedphysical route in a process control system, wherein the process controlsystem includes a wireless gateway network device and a plurality ofprocess devices in wireless communication with the wireless gatewaynetwork device, the method implemented via one or more processors, themethod comprising: determining a signal strength of a wirelessconnection between each process device and the wireless gateway networkdevice and/or between each process device and another process device;for each process device, beginning with the first process device, in aninitial list of process devices in direct wireless communication withthe wireless gateway network device, where the process devices of theinitial list are ranked therein according to a signal strength of awireless connection with the wireless gateway network device,iteratively selecting the process devices from the initial list; witheach iteration, appending the initial list with the remaining processdevices from the plurality of process devices until the plurality ofprocess devices are included in the appended initial list by: creating asubsequent list of process devices in direct wireless communication withthe process device selected from the initial list, wherein the processdevices of the subsequent list are ranked therein according to a signalstrength of a wireless connection with the process device selected fromthe initial list; and appending the initial list with the processdevices in the subsequent list, wherein each process device appended tothe initial list is ranked therein after the process device selectedfrom the initial list according to the signal strength of its wirelessconnection with the process device selected from the initial list,unless the process device from the subsequent list is already ranked inthe initial list ahead of the selected process device from the initiallist, generating an ordered physical route of traversal through theplurality of process devices according to the order of the plurality ofprocess devices in the appended list; and displaying the orderedphysical route of traversal.
 2. The method of claim 1 further comprisingcreating the initial list of process devices in direct wirelesscommunication with the wireless gateway network device, where theprocess devices of the initial list are ranked therein according to thesignal strength of the wireless connection between each process devicein the initial list and the wireless gateway network device, with highersignal strengths ranked ahead of weaker signal strengths.
 3. The methodof claim 1, wherein for a process device from the subsequent list thatis already ranked in the initial list from a previous iteration of theinitial list, appending the initial list comprises re-ranking thealready-ranked process device in the initial list after the selectedprocess device from the initial list according to the signal strength ofits wireless connection with the process device selected from theinitial list.
 4. The method of claim 1, further comprising measuring thesignal strength of a wireless connection between each process device indirect wireless communication with the wireless gateway network deviceand the wireless gateway network device, wherein the signal strength isinterpreted as correlating to the physical proximity of the processdevice to the wireless gateway network device.
 5. The method of claim 1,further comprising measuring the signal strength of a wirelessconnection between each process device in direct wireless communicationwith another process device, wherein the signal strength is interpretedas correlating to the physical proximity of the process devices.
 6. Themethod of claim 1, wherein a start of the ordered physical routecomprises the physical location within the process control system of theprocess device first listed in the appended initial list, wherein theprocess device first listed in the appended initial list corresponds tothe process device having the strongest signal strength with thewireless network gateway device.
 7. The method of claim 1, furthercomprising displaying the ordered physical route on a display screen ofa client computing device.
 8. The method of claim 7, wherein the clientcomputing device comprises a handheld device.
 9. The method of claim 1,further comprising mapping the ordered physical route over a map of theprocess control system.
 10. The method of claim 1, further comprisingidentifying process devices along a communication route within awireless network, wherein each of the process devices in the initiallist comprises a first process device along a communication route fromthe wireless network gateway device.
 11. The method of claim 10, whereinidentifying process devices along a communication route within thewireless network comprises identifying process devices along acommunication route within the wireless network using traceroute.
 12. Amethod of generating an ordered physical route in a process controlsystem, wherein the process control system includes a wireless networkcomprising a wireless gateway network device and a plurality of wirelessnetwork nodes, each of which is in wireless communication with thewireless gateway network device either directly or via another wirelessnetwork node, the method implemented on one or more processors, themethod comprising: determining a signal strength of a wirelessconnection between each wireless network node and the wireless gatewaynetwork device and/or between each wireless network node and anotherwireless network node; creating a primary ordered list of wirelessnetwork nodes in direct wireless communication with the wireless gatewaynetwork device, wherein the wireless network nodes comprising theprimary ordered list are organized according to decreasing signalstrength with the wireless gateway network device; iteratively appendingthe primary ordered list with the remaining wireless network nodes,wherein each iteration comprises: selecting a wireless network node fromthe previous iteration of the primary ordered list; creating a secondaryordered list of wireless network nodes in direct wireless communicationwith the selected wireless network node, wherein the wireless networknodes comprising the secondary ordered list are organized according todecreasing signal strength with the selected wireless network node; andappending the primary ordered list with the wireless network nodes ofthe secondary ordered list after the selected wireless network node,generating an ordered physical route of traversal through the pluralityof process devices according to the order of the plurality of processdevices in the appended list; and displaying the ordered physical routeof traversal.
 13. The method of claim 12, wherein creating a primaryordered list comprises: selecting a wireless network node from among theplurality of wireless network nodes; determining the hop count of theselected wireless network node with respect to the wireless gatewaynetwork device; adding the selected wireless network node to the end ofthe primary ordered list if the hop count is zero; comparing a receivedsignal strength indicator (RSSI) of the selected wireless network nodeto an RSSI of a wireless network node preceding the selected wirelessnetwork node in the primary list; and re-organizing the primary list torank the selected wireless network node ahead of the preceding wirelessnetwork node if the RSSI of the selected wireless network node isgreater than the RSSI of the preceding wireless network node.
 14. Themethod of claim 12, wherein creating a secondary ordered list comprises:selecting a wireless network node from among the plurality of wirelessnetwork nodes; determining the hop count of the selected wirelessnetwork node with respect to the wireless network node selected from theprevious iteration of the primary ordered list; adding the selectedwireless network node to the end of the secondary ordered list if thehop count is zero; comparing a received signal strength indicator (RSSI)of the selected wireless network node from the plurality of wirelessnetwork nodes to an RSSI of a wireless network node preceding theselected wireless network node from the plurality of wireless networknodes in the secondary ordered list; and re-organizing the secondaryordered list to rank the selected wireless network node from theplurality of wireless network nodes ahead of the preceding wirelessnetwork node if the RSSI of the selected wireless network node from theplurality of wireless network nodes is greater than the RSSI of thepreceding wireless network node.
 15. The method of claim 12, whereinappending the primary ordered list comprises: selecting a wirelessnetwork node from the secondary ordered list; determining whether thewireless network node selected from the secondary ordered list isalready ranked above the wireless network node selected from theprevious iteration of the primary ordered list in the previous iterationof the primary ordered list; determining whether the wireless networknode selected from the secondary ordered list is already ranked in theprevious iteration of the primary ordered list if the wireless networknode selected from the secondary ordered list is not ranked above thewireless network node selected from the previous iteration of theprimary ordered list in the previous iteration of the primary orderedlist; adding the wireless network node selected from the secondaryordered list to the primary ordered list after the wireless network nodeselected from the previous iteration of the primary ordered listaccording to the order of wireless network nodes in the secondaryordered list if the wireless network node from the secondary orderedlist is not already ranked in the previous iteration of the primaryordered list; and re-organizing the primary ordered list to rank thewireless network node selected from the secondary ordered list after thewireless network node selected from the previous iteration of theprimary ordered list according to the order of wireless network nodes inthe secondary ordered list if the wireless network node from thesecondary ordered list is already ranked in the previous iteration ofthe primary ordered list.
 16. The method of claim 12, wherein a start ofthe ordered physical route comprises the physical location within theprocess control system of the process device corresponding to thewireless network node first listed in the appended primary ordered list,wherein the wireless network node first listed in the appended primaryordered list corresponds to the wireless network node having thestrongest signal strength with the wireless network gateway device. 17.The method of claim 12, further comprising displaying the orderedphysical route on a display screen of a client computing device.
 18. Themethod of claim 17, wherein the client computing device comprises ahandheld device.
 19. The method of claim 12, further comprising mappingthe ordered physical route over a map of the process control system. 20.A system for automatically generating an ordered physical route in aprocess control system, wherein the process control system includes awireless gateway network device and a plurality of wireless networknodes in wireless communication with the wireless gateway networkdevice, the system comprising: a server comprising a processor, a memoryoperatively coupled to the processor and a server communicationtransceiver; client computing device comprising a display, amicroprocessor and a wireless transceiver communicatively coupled to theserver via the wireless transceiver; a routine stored in the memory andadapted to be executed by the processor to determine a signal strengthof a wireless connection between each wireless network node and thewireless gateway network device and/or between each wireless networknode and another wireless network node; a routine stored in the memoryand adapted to be executed by the processor to iteratively selectwireless network nodes from an initial list of wireless network nodes indirect wireless communication with the wireless gateway network devicebeginning with the first wireless network node, where the wirelessnetwork nodes of the initial list are ranked therein according to asignal strength of a wireless connection with the wireless gatewaynetwork device; a routine stored in the memory and adapted to beexecuted by the processor to, for each iteration, create a subsequentlist of wireless network nodes in direct wireless communication with thewireless network node selected from the initial list, wherein thewireless network nodes of the subsequent list are ranked thereinaccording to a signal strength of a wireless connection with thewireless network node selected from the initial list; a routine storedin the memory and adapted to be executed by the processor to, for eachiteration, append the initial list with the wireless network nodes inthe subsequent list, wherein each wireless network node appended to theinitial list is ranked therein after the wireless network node selectedfrom the initial list according to the signal strength of its wirelessconnection with the wireless network node selected from the initiallist, wherein the appended initial list including the plurality ofwireless network nodes relates to an ordered physical route among theprocess devices; a routine stored in the memory and adapted to beexecuted by the processor to generate an ordered physical route oftraversal through the plurality of process devices according to theorder of the plurality of process devices in the appended list; and aroutine stored in the memory and adapted to be executed by the processorto display the ordered physical route of traversal.
 21. The system ofclaim 20, further comprising a routine stored in the memory and adaptedto be executed by the processor to create the initial list of wirelessnetwork nodes in direct wireless communication with the wireless gatewaynetwork device, wherein the wireless network nodes comprising theinitial list are organized according to decreasing signal strength withthe wireless gateway network device.
 22. The system of claim 20, whereinthe routine to create the initial list of wireless network nodescomprises: a routine stored in the memory and adapted to be executed bythe processor to select a wireless network node from among the pluralityof wireless network nodes; a routine stored in the memory and adapted tobe executed by the processor to determine the hop count of the selectedwireless network node with respect to the wireless gateway networkdevice; a routine stored in the memory and adapted to be executed by theprocessor to add the selected wireless network node to the end of theinitial list if the hop count is zero; a routine stored in the memoryand adapted to be executed by the processor to compare a wirelessconnection signal strength of the selected wireless network node to awireless connection signal strength of a wireless network node precedingthe selected wireless network node in the initial list; and a routinestored in the memory and adapted to be executed by the processor tore-organize the initial list to rank the selected wireless network nodeahead of the preceding wireless network node if the wireless connectionsignal strength of the selected wireless network node is greater thanthe wireless connection signal strength of the preceding wirelessnetwork node.
 23. The system of claim 20, wherein the routine stored tocreate a subsequent list comprises: a routine stored in the memory andadapted to be executed by the processor to select a wireless networknode from among the plurality of wireless network nodes; a routinestored in the memory and adapted to be executed by the processor todetermine the hop count of the selected wireless network node withrespect to the wireless network node selected from the previousiteration of the initial list; a routine stored in the memory andadapted to be executed by the processor to add the selected wirelessnetwork node to the end of the subsequent list if the hop count is zero;a routine stored in the memory and adapted to be executed by theprocessor to compare a wireless connection signal strength of theselected wireless network node from the plurality of wireless networknodes to a wireless connection signal strength of a wireless networknode preceding the selected wireless network node from the plurality ofwireless network nodes in the subsequent list; and a routine stored inthe memory and adapted to be executed by the processor to re-organizethe subsequent list to rank the selected wireless network node from theplurality of wireless network nodes ahead of the preceding wirelessnetwork node if the wireless connection signal strength of the selectedwireless network node from the plurality of wireless network nodes isgreater than the wireless connection signal strength of the precedingwireless network node.
 24. The system of claim 20, wherein the routinestored to append the initial list comprises: a routine stored in thememory and adapted to be executed by the processor to select a wirelessnetwork node from the subsequent list; a routine stored in the memoryand adapted to be executed by the processor to determine whether thewireless network node selected from the subsequent list is alreadyranked above the wireless network node selected from the previousiteration of the initial list in the previous iteration of the initiallist; a routine stored in the memory and adapted to be executed by theprocessor to determine whether the wireless network node selected fromthe subsequent list is already ranked in the previous iteration of theinitial list if the wireless network node selected from the subsequentlist is not ranked above the wireless network node selected from theprevious iteration of the initial list in the previous iteration of theinitial list; a routine stored in the memory and adapted to be executedby the processor to add the wireless network node selected from thesubsequent list to the initial list after the wireless network nodeselected from the previous iteration of the initial list according tothe order of wireless network nodes in the subsequent list if thewireless network node from the subsequent list is not already ranked inthe previous iteration of the initial list; and a routine stored in thememory and adapted to be executed by the processor to re-organize theinitial list to rank the wireless network node selected from thesubsequent list after the wireless network node selected from theprevious iteration of the initial list according to the order ofwireless network nodes in the subsequent list if the wireless networknode from the subsequent list is already ranked in the previousiteration of the initial list.
 25. The system of claim 20, wherein astart of the ordered physical route comprises the physical locationwithin the process control system of the process device corresponding tothe wireless network node first listed in the appended initial list,wherein the wireless network node first listed in the appended initiallist corresponds to the wireless network node having the strongestsignal strength with the wireless network gateway device.
 26. The systemof claim 20, further comprising a routine stored in the client computingdevice and adapted to be executed by the microprocessor to display theordered physical route on the display.
 27. The system of claim 20,further comprising a routine stored in the memory and adapted to beexecuted by the processor to map the ordered physical route over a mapof the process control system.